A141888 Primes congruent to 2 mod 21.

2, 23, 107, 149, 191, 233, 317, 359, 401, 443, 569, 653, 821, 863, 947, 1031, 1283, 1367, 1409, 1451, 1493, 1619, 1787, 1871, 1913, 1997, 2039, 2081, 2207, 2333, 2417, 2459, 2543, 2711, 2753, 2837, 2879, 2963, 3089, 3257, 3299, 3467, 3593, 3677, 3719, 3761

Offset: 1

Author

N. J. A. Sloane, Jul 11 2008

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040.

Programs

Magma

[p: p in PrimesUpTo(4000) | p mod 21 eq 2 ]; // Vincenzo Librandi, Aug 16 2012

Mathematica

Select[Prime[Range[600]], Mod[#,21] == 2&] (* Harvey P. Dale, Jan 04 2011 *)

PARI

is(n)=isprime(n) && n%21==2 \\ Charles R Greathouse IV, Jul 02 2016

Formula

a(n) ~ 12n log n. - Charles R Greathouse IV, Jul 02 2016